The present invention relates to a tool for the removal or installation of threaded fasteners, particularly for use in situations where it is important that a bit driving the fastener not slip from the head of the fastener.
Many threaded fasteners require a bit to be pressed firmly into a socket on the fastener in order to loosen or tighten the fastener. This is especially true when the fastener is driven by a bit that engages a socket with inclined surfaces such as are formed on the heads of Phillips head screws. Difficulties may be encountered in keeping a tool such as a Phillips bit screwdriver in place. Difficulties may be encountered even when the driven surfaces of the fastener socket are straight walled such as Allen or other socket head screws. The bit driving the fastener can slip out when torque is applied especially when the axis of the bit is misaligned with the axis of the fastener. When the bit slips out of the screw head, it may cause damage to surrounding components. Further, workers who must press downward with considerable pressure on a screwdriver or other tool to keep it from popping out of the head of a screw may find the task difficult, awkward, or injurious. The recognition of these problems arose in the context of removing screws from the surfaces of missiles or aircraft, for example, to remove cover plates to obtain access to interior components, but the solution to these problems has much broader applications.
The tool is used to turn a threaded fastener while assuring that the bit that engaging the fastener does not slip out of the head of the fastener. This reduces the risk of damaging surrounding components. The tool includes any one of a variety of pivot assemblies, and which one is used depends upon what nearby surfaces are available to mount the pivot assembly. Generally, the pivot assembly may be screwed into a surface adjacent the screw to be turned. A lever is connected to the pivot assembly. The lever carries a hub assembly which is slidable along the length of the lever, and the lever has a handle at one end. The pivot assembly allows the lever to sweep in a circle about its axis and also to be lifted up and down with respect to the surface which holds the screw to be turned. The hub assembly includes a drive end which may be either an integrally formed bit or a conventional attachment for an interchangeable bit. The hub assembly also includes driven surfaces to allow a conventional wrench to be used to turn the bit. In use, the hub assembly is positioned over the screw to be turned with the bit aligned with the screw. Thereafter the worker presses the handle of the lever downward to hold the bit properly aligned and correctly seated in the head of the screw. Once properly positioned, the bit is turned by using a wrench on the hub assembly.